Process for the manufacture of highly pure phenol by distillation in the presence of excess cumene



1968 MASAYUKI KOHMOTO 3,405,038

PROCESS FOR THE MANUFACTURE OF HIGHLY PURE PHENOL BY DISTILLATION IN THEPRESENCE OF EXCESS CUMENE I v Filed April 25, 1967 Acetone AcetoneTopper Oxldizer Concentrating I zone 6 Acetone Column Crude AcetoneColumn Additional Cumene+ Cumene 5 Water Air 1 Clude H2504 Phenol 1Column Cumene Cleavage Vessel High" Column INVENTOR. M ASAYU Kl KOHMOTOUnited States Patent 3,405,038 PROCESS FOR THE MANUFACTURE OF HIGHLYPURE PHENOL BY DISTILLATION IN THE PRES- ENCE 0F EXCESS CUMENE MasayukiKohmoto, Ohtak shi, Japan, assignor to Mitsui Petrochemical Industries,Ltd., Tokyo, Japan Continuation-impart of application Ser. No. 320,940,Nov. 1, 1963. This application Apr. 25, 1967, Ser. .No. 633,605 Claimspriority, application Japan, Mar. 27, 1963,

38/ 13,881 2 Claims. (Cl. 203-69) ABSTRACT OF THE DISCLOSURE Process forproducing apurified phenol :from a conventional oxidative-cumene processby adjusting the remaining cumene to phenol ratio so that it is within arange of 0.28:1 to 1:1 prior toa first distillation step to remove thoseproducts boiling at a lower boiling point than phenol thereaftersubjecting the residue to a second distillation step to remove thephenol in the overhead fraction.

This application is a continuation-in-part of copending application Ser.No. 320,940, filed on Nov. 1, 1963, now abandoned.

The present invention relates to a process for the production of highlypure phenol by so-called cumene process, more particularly to a processfor the production of highly pure phenol from a crude phenol which isobtained by the oxidation of cumene followed by the cleavage of cumenehydroperoxide thus formed.

BACKGROUND OF THE INVENTION There have already been proposed variousprocesses. on

. industrial scale for the production of phenol by the oxidation ofcumene, subsequent cleavage of cumene hydroperoxide and distillation ofthe cleavage reaction product. In the oxidation step, it is usual tomaintain the degree of oxidation of cumene to cumene hydroperoxide toabout to of the theoretical value to prevent the reaction system fromthe decomposition of cumene hydroperoxide and from the risk ofexplosition (cf. British Patent No. 649,286). The oxidation reactionproduct is usually subjected to a distillation, before it is subjectedto the subsequent cleavage reaction to remove most of the unreactedcumene therefrom, thus it is possible to reduce the dimensions ofapparatus for the cleavage reaction and subsequent distillation and tominimize the operating cost therefor (of. US. Patent No. 2,986,583).After the cleavage reaction of cumene hydroperoxide in the presence ofan acid catalyst, the cleavage reaction product is washed with water toremove the acid catalyst and then sent to a purification step.

The cleavage reaction product is mainly composed of phenol, acetone,water and cumene and further contains various impurities, typicallyacetophenone, pheny-l dimethyl car'binol, acetaldehyde, p-cumylphenol,a-methylstyrene, mesityl oxide, hydroxyacetone, acetoin, 2-methylbenzofuran, 2,3-dimethyl benzofuran .and the like. Among theseimpurities, a-hydroxycarbonyl compounds represented by the generalformula:

where R, and R each represent hydrogen or alkyl group, typicallyhydroxyacetone and acetoin and benzofuran derivatives which arecondensation products of tar-hydroxycarbonyl compounds with phenol,typically 2-rnethyl benzofuran and 2,3-dimethyl benzofuran are generally3,405,038 Patented Oct. 8, 1968 ice considered to be a factor to causean undesirable color formation when the phenol containing suchimpurities is subjected to chlorination or sulfonation. If phenol isused as starting material for synthetic fibre manufacture, therefore, itis required for the phenol to have such a high purity as substantiallyfree from these impurities.

In order to isolate a desired product or products from the cleavagereaction product, it is conventional to take a method wherein acetone,water and low-boiling impurities are first distilled off as overheadfraction leaving phenol, unreacted cumene and high-boiling impurities asbottom residue which is then distilled to isolate the phenol or a methodwherein acetone, water, unreacted cumene and low-boiling impurities arefirst distilled off as overhead fraction, leaving phenol andhigh-boiling impurities as bottom residue which is then distilled toisolate the phenol.

As examples of the former method, there may be mentioned US. Patent No.2,824,048 to Hupe et al. and U .5. Patent No. 2,862,855 to Lang et .211.both of which relate to such improvement that after the removal ofacetone, the bottom residue is further distilled with the addition oflarge amount of water thereby to remove effectively cumene andmethylstyrene from phenol. However, by such a method, it is impossibleto remove trace impurities such as hydroxy acetone and 2,3-dimethylbenzofuran from phenol.

An example of the latter method is described in US. Patent No. 3,169,101to Berthoux which relates to a process wherein after the removal ofacetone and cumene by a conventional simple distillation, the bottomresidue containing impure phenol is distilled with the addition of asolvent boiling higher than phenol such as diethylene glycol anddiethylene glycol monobutyl ether to facilitate the effective removal ofimpurities from phenol. This method may achieve the effective removal ofremaining cumene, tit-methylstyrene, mesityl oxide, Z-methyl benzofuranand hydroxyacetone, but necessitates a large-sized plant due to the useof an additional solvent having a higher boiling point than that ofphenol in a larger amount than that of phenol present and alsonecessitates an additional step for the recovery of said solvent.Therefore, even if a highly pure phenol is obtained by this method, theproduction cost hereof is fairly high.

SUMMARY OF THE INVENTION The object of the present invention is toprovide an improvement in the process for the production of phenol bydistillation of a crude phenol obtained by the oxidation of cumenefollowed by the cleavage of cumene hydroperoxide; the principle uponwhich the present invention is based is substantially different fromthat of such a known extractive distillation with the addition of aparticular solvent as used in the above-mentioned process. That is, thepresent invention intends to remove troublesome color-forming impuritiestogether with the removal of acetone and cumene in a single distillationstep under a controlled condition, leaving phenol containing highboiling impurities which can be easily removed from phenol by asubsequent simple distillation and thus the production of phenol havingexceptionally high purity free from troublesome impurities, particularlyfrom ochydroxycarbonyl compounds can be achieved very easily andeconomically.

According to the present invention, in a process for the production ofphenol by the oxidation of cumene, subsequent cleavage of cumenehydroperoxide and distillation of the cleavage reaction product, thereis provided an improvement which comprises subjecting the cleavagereaction product which consists of phenol, acetone, cumene, water andother impurities including ahydroxycarbonyl compounds the presence ofwhich causes undesirable color formation on chlorination and sulfonation of the phenol to a distillation, with no previous distillation stepfor removal of acetone, in such a manner that the content of cumene inthe feed for the distillation is maintained to a value at least 0.28part by weight of cumene per part by weight of phenol contained thereinand that the temperature at a point in the distillation column above thefeeding point of the feed is maintained at a value from 110 C. to theboiling point of cumene at atmospheric pressure in order to distill offcompletely acetone, cumene, water, a-hydroxycarbonyl compounds and otherlow boilers as overhead fraction which is practically free from phenoland then subjecting the residual mixture consisting substantially ofphenol and high boilers to a distillation to isolate a highly purephenol from the high boilers.

BRIEF DESCRIPTION OF THE DRAWING The single figure of the drawing is asimplified schematic diagram of the process according to the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a preferred embodiment forcarrying out the process of the present invention, the cleavage reactionproduct which usually contains 25-50% by weight of phenol and 2050% byweight of acetone is, after the content of cumene therein is adjusted toat least 0.28 part by weight per part of phenol, introduced into adistillation column in which the temperature at a point upper than thefeeding point of the feed by at least five plates is maintained at avalue ranging from 130 C. to the boiling point of cumene at atmosphericpressure. Thus, according to the present invention, it is possible toremove directly from the cleavage reaction product not only acetone,cumene and water, but also troublesome color-forming impurities,typically a-hydroxycarbonyl compounds as overhead fraction, leavingphenol practically completely free from such color-forming impurities asbottom fraction.

As the feed to the distillation according to the present invention, itis preferred to use a crude phenol which was obtained by the oxidationof cumene, concentration of cumene hydroperoxide thus formed to theconcentration of 70-80%, cleavage of cumene hydroperoxide in thepresence of an acid catalyst, removal of the catalyst and washing thecleavage reaction product with water. Such a crude phenol will containall the cleavage reaction products, that is acetone, phenol, water andvarious impurities including a-hydroxy carbonyl compounds and unreactedcumene. One of the characteristic features of the present invention isto use as the feed to the distillation such a crude phenol, that is thecleavage reaction product from which no acetone has been removed; thisis based on my discovery that the presence of acetone in the feed isadvantageous to obtain a very highly pure phenol. The use of a crudephenol containing 20 to 50% by weight of acetone is most preferred.Another characteristic feature of the present invention is that thepresence of cumene in an amount at least 0.28 part by weight per part byweight of phenol contained in the feed is essential to maintain thetemperature at a point in the distillation column above the feedingpoint of the feed at a value from 110 C. to the boiling point of cumeneat atmospheric pressure. If the content of cumene is less than 0.28 partby weight per part by weight of phenol, it is difficult to maintain thetemperature at that point at the specified value thereby to make asteady distilling operation impossible and to make the removal ofcolorforming impurities insufiicient. The upper limit of the content ofcumene is not particularly critical, but it is preferred from theeconomical point of view for the capacity of apparatus to use thecontent of cumene not greater than the content of phenol. When the feed,crude phenol, contains cumene in an amount less than 0.28 part by Weightper part by weight of phenol, additional cumene is to be supplied to thefeed through the supply pipe of the feed or to the column through aninlet point positioned near the feeding point of the feed to maintainthe content of cumene at a value at least 0.28 part by weight per partby weight of phenol as the whole contained in the distillation column.

The distillation according to the present invention may be carried out'at atmospheric pressure or a reduced pressure.

The process of the present invention is further illustrated by referringto the accompanying drawing in which a typical embodiment of the presentinvention is shown.

Air and cumene each are introduced into oxidation reactor 1. Cumenehydroperoxide formed in the reactor 1 is introduced into concentratingzone 2, from which unreacted cumene is recycled to the reactor 1. Afluid containing 'a major proportion of cumene hydroperoxide is thensent to cleavage reaction vessel 3 in which the cumene hydroperoxide iscleaved into acetone and phenol. Liquid eflluent from the cleavagevessel 3 is neutralized and washed with water in water wash zone 4.Liquid elfiuent from the water wash zone 4 is fed into distillationcolumn 5 referred to as crude acetone column in which it is separatedinto an overhead fraction containing acetone, c umene, water and lowboiling impurities including a-hydroxycarbonyl compounds and a bottomfraction containing phenol and high boiling impurities. The overheadfraction is introduced into acetone topper 6 in which low boilingimpurities are removed and then sent to acetone column 7 in which pureacetone is isolated as overhead fraction, leaving cumene and water asbottom fraction. The bottom fraction from the crude acetone column 5 ispassed through crude phenol column 8 in which higher boiling impuritiesare removed and then sent to phenol topper 9 in which remaining lowboiling impurities are removed as overhead fraction. Bottom fractionfrom the phenol topper 9 is finally introduced into phenol column 10 inwhich pure phenol is isolated as overhead fraction from remaining highboiling impurities.

The present invention is illustrated, but not limited, by the followingexamples.

Example I Cumene hydroperoxide mixture obtained by oxidation of cumenewas cleaved in the presence of an acid catalyst and then the catalystwas removed by washing and neutralizing in a conventional manner. Inorder to separate the resulting product into an overhead fractioncontaining acetone, water, cumene and high boiling impurities and abottom fraction containing phenol and higher boiling impurities, acontinuous distillation column of 45 trays operated at atmosphericpressure was used. The feed, which contained 40% acetone, 36% phenol, 8%cumene, 11% water, 5% others (each wt. percent, the ratio of phenol tocumene=l.0.22) and 1380 p.p.m. hydroxyacetone, was introduced into the15th tray from the bottom at a rate of 7,000 l./hr., maintaining thebottom temperature at 191 C. and the top temperature at 82 C.

Cumene was added to the feed at a rate of 250-350 l./hr., at the sametime adjusting the temperature at the 17th through 35th trays from thebottom of column at a value between 130 C. and 135 C. (the ratio ofphenol to cumene=1:0.330.36). The temperature of 40th tray wasmaintained at C., and the bottom product contained as little as 60p.p.m. hydroxyacetone.

By contrast, when no additional cumene was added to the feed, althoughthe top and bottom temperature remained unchanged, the temperature ofthe trays mentioned above could not be maintained at C.- C. and droppedto about 90 C., increasing the hydroxyacetone content of the bottomproduct to as much as 900 p.p.m.

Example II To the same continuous distillation column of 45 trays and atatmospheric pressure as described in Example I, the feed, whichcontained 38% acetone, 35% phenol, 9.5% cumene, 12% water, 5.5% others(each wt. percent, the ratio of phenol to cumene=1:0.27) and 1500 p.p.m.hydroxyacetone, was introduced into the 25th tray from the bottom at arate of 7000 l./hr., maintaining the bottom temperature at 191 C. andthe top temperature at 79 C. Cumene was added to the feed at a rate of-1 00- 200 l./hr., (the ratio of phenol to cumene=1:0.31-0.35),maintaining the temperature of the 27th through 35th trays from thebottom at 130 C.-135 C., and the bottom product contained only 30 p.p.m.hydroxyacetone.-

However, when no additional cumene was added, the temperature of the27th through 40th trays dropped to 88 C.-90 C. as against 80 C. at thetop and 191 C. at the bottom, and the hydroxyacetone content of thebottom product increased as much as to 970 p.p.m.

Example III To the same continuousdistillation column of 45 trays and atatmospheric pressure as described in Example I, the feed, whichcontained 34% acetone, 30% phenol, 19% cumene, 11% water, 6% others(each wt. percent, the ratio of the phenol to cumene=1:0.63) and 1300p.p.m. hydroxyacetone, was introduced into the 20th tray from the bottomat a rate of 6500 l./ hr. In this case, the temperature of the 22ndthrough 35th trays from the bottom could be maintained at a valuebetween 130 C. and 140 C. without adding cumene to the feed, and thebottom product contained only 65 p.p.m. hydroxyacetone.

Example IV To the same continuous distillation column of 45 trays and atatmospheric pressure as described in Example I, the feed, whichcontained 27% acetone, 46% phenol, 12% cumene, 9% water, 6% others (eachwt. percent, the ratio of the phenol to cumene=1:0.26) and 1,500 p.p.m.hydroxyacetone, was introduced into the 20th tray from the bottom at arate of 4900 1./hr., maintaining the bot- 6 tom temperature at 190 C.and the top temperature at 81 C.

Cumene was added to the feed at a rate of -140 l./hr. (the ratio of thephenol to cumene=1:0.28-0.32), maintaining the temperature of the 22ndthrough 35th trays from the bottom at 140153 C., and the bottom productcontained p.p.m. hydroxyacetone, and the temperature of the 40th tray atthat time was 112 C. From this, it was ascertained that the temperaturedistribution as above is sufiicienly elfective even when the feedcontained considerably higher proportion of phenol than acetone.

I claim:

1. The process for the removal from impure phenol produced by thecleavage of cumene hydroperoxide, of impurities, including traceimpurities, the presence of which causes undesirable color formation onchlorination and sulfonation of the phenol, which comprises adjustingthe impure phenol by the addition of cumene in a quantity to achieve aratio of at least 0.28 part by weight cumene to one part by weight ofphenol in the impure phenol, then subjecting the impure phenol to afirst distillation step in a distillation column wherein the temperaturein the column above the feed point is maintained from C. up to theboiling point of cumene whereby the impurities having boiling points upto and including cumene are distilled, thereafter subjecting the therebypartially purified phenol to a second distillation step at a temperaturejust sufficient to distill the phenol from impurities having higherboiling points than said phenol.

2. The process of claim 1 wherein the cumene is added in a quantity toachieve a range of ratios of cumene to phenol of from 0.28:1 to 1:1.

References Cited UNITED STATES PATENTS 2,824,048 2/1958 Hupe et al.260-621 2,862,855 12/1958 Lang et a1 26062l 2,992,169 7/ 1961 Gregory etal 26062-1 3,169,101 2/ 1965 Berthoux 203-59 WILBUR L. BASCOMB, .IR.,Primary Examiner.

